Circumferential flow pump

ABSTRACT

A circumferential flow pump in which the quantity of swelling by alcohol or toluene contained in fuel, is curbed and an impeller thereof is prevented from locking is provided. 
     A circumferential flow pump for feeding into an internal combustion engine, fuel from the fuel tank thereof includes an impeller, made of fiber-reinforced PPS, having a base portion fitted to a motor rotor, a vane portion provided outer-circumferentially on the base portion, and an outer ring portion provided outer-circumferentially on the vane portion; the vane portion is composed of a plurality of vanes arranged radially protruding straightly from the base portion and each vane includes a bend thereon; and furthermore, given that a projected area of the entire vane portion is S 1 , that of the ring portion, S 2 , that of the base portion, S 3 , when the impeller, is projected from a direction along a motor shaft of the motor rotor, the ratio of S 3  to S 1  is made to fall between 9:1 to 15:1, and the ratio of S 2  to S 1  is made to fall between 0.10:1 to 0.13:1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to circumferential flow pumps that are housed in the fuel tank of, for example, an automobile, and supply fuel to the internal combustion engine thereof at a predetermined pressure.

2. Description of the Related Art

An impeller mounted on a circumferential flow pump is provided with a base portion that is fitted to a motor rotor, a vane portion that is formed outer-circumferentially on the base portion, and an outer ring portion that is formed outer-circumferentially on the vane portion. In conventional circumferential flow pumps, impellers have being developed for the purpose of raising efficiency or lowering noise. As an impeller of this king, it is known that the vane portion is made thinner, and that fiber-reinforced polyphenylene sulfide(PPS), being excellent in moldability and dimensional stability, is used. It is also known that a bend is formed on each vane (e.g., Japanese Patent Laid-Open No. 2003-336558).

SUMMARY OF THE INVENTION

In conventional circumferential flow pumps, resin's flow during injection molding tends to be blocked due to bends on the vane portion. When fiber-reinforced PPS is used as the molding resin, the orientation of the fiber, being reinforcing material, tends to be uniform at the bends of the vane portion. During the injection molding, the molding resin is injected through the vane portion into the outer ring portion, in which fiber's orientation tends to be uniform also in the ring under the effect of the vane portion. It is effective to enhance randomness of the fiber-orientation or enhance crystallinity of the fiber-reinforced PPS, in order to curb its swelling by alcohol and toluene that are contained in fuel. In the base portion, dwelling operation during the injection molding can enhance the crystallinity of the PPS, but in the vane portion and the ring portion, the dwelling pressure cannot be transferred thereto to such an extent that the crystallinity thereof can be enhanced. Consequently, due to the low randomness of fiber-orientation in the vane portion and the ring portion, the quantity of swelling thereof by alcohol and toluene becomes large compared with that in the base portion. When the impeller swells so much as to contact with a pump-housing, there arises a problem in that the impeller locks.

To curb the quantity of the swelling, it might be an alternative way to use a thermosetting resin, such as a phenolic resin, however, operations in later processes, such as deburring, become necessary.

The present invention is made in order to solve above-described problems and provide a circumferential flow pump, in which the impeller mounted on the circumferential flow pump is made of fiber-reinforced PPS, so as to curb the quantity of swelling by alcohol and toluene contained in the fuel, so that the impeller is prevented from locking.

In the present invention, a circumferential flow pump that feeds into an internal combustion engine, fuel from a fuel tank, includes:

a disc-shaped impeller fitted to a motor rotor, and

a pump-housing for housing the impeller; wherein the impeller is made of fiber-reinforced PPS and composed of a base portion fitted to a motor rotor,

a vane portion provided outer-circumferentially on the base portion, and

an outer ring portion provided outer-circumferentially on the vane portion, and the vane portion is composed of a plurality of vanes arranged radially protruding straightly from the base portion and each vane includes a bend; and furthermore, given that a projected area of the entire vane portion is S1, that of the ring portion, S2, that of the base portion, S3, when the impeller is projected from a direction along the shaft of the motor rotor, the ratio of S3 to S1 is made to fall between 9:1 and 15:1, and the ratio of S2 to S1 is made to fall between 0.10:1 and 0.13:1.

According to the present invention, because a circumferential flow pump having an impeller made of fiber-reinforced PPS is provided, the quantity of swelling by alcohol and toluene contained in the fuel can be curbed, so that a circumferential flow pump can be provided in which the impeller is prevented from locking.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectional elevation view illustrating a circumferential flow pump in Embodiment 1;

FIG. 2 a and FIG. 2 b are perspective views illustrating the impeller in Embodiment 1; FIG. 2 a is a whole view thereof, and FIG. 2 b is a partially sectional view thereof;

FIG. 3 is a characteristic diagram showing the swelling quantity of the impeller by alcohol and toluene.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1 is a partially sectional elevation view illustrating a circumferential flow pump in Embodiment 1. The circumferential flow pump 1 includes: a disc-shaped impeller 2 fitted to the motor rotor 3; and a pump-housing 7, composed of a pump cover 5 and a pump base 6 for housing the impeller 2. In the pump cover 5, a thrust bearing 5 a is placed at the center thereof for bearing in the thrust direction the shaft of the motor rotor 3, and an inlet 5 b is provided at the bottom of the cover for leading from a fuel tank, fuel into the impeller 2. At the center of the pump base 6, a metal member 6 a is placed for bearing the rotating shaft of the rotor 3.

When the motor rotor 3 is driven with the pump 1 being immersed in the fuel tank, the fuel is led from the inlet 5 b into the pump room by the rotation of the impeller 2. Through an outlet 6 e of a pump room and the motor room, the fuel is sent from a spout 4 to the internal combustion engine. In addition, in order to prevent the rotation of the impeller 2 from being hampered, a clearance 7 a is provided between the impeller 2 and the pump-housing 7.

FIG. 2 a and FIG. 2 b are perspective views illustrating the impeller 2; FIG. 2 a is a whole view thereof, and FIG. 2 b is a partially sectional view thereof. The impeller 2 includes a base portion 2 a fitted to the motor rotor 3, a vane portion 2 b formed outer-circumferentially on the base portion 2 a, and an outer ring portion 2 c formed outer-circumferentially on the vane portion 2 b. At the center of the base portion 2 a, an insertion hole 2 f, being shaped into the capital letter D, is formed for being fitted to the shaft of the rotor 3. The vane portion 2 b is composed of a plurality of vanes arranged radially protruding straightly from the base portion 2 a. The vanes on the vane portion 2 b are molded into less than 0.5 mm in thickness, and each vane has a bend 2 e, which is shown in FIG. 2 b.

Although the shape of the impeller 2 varies due to specifications of the circumferential flow pump, it is assumed in the following description that the diameter of the impeller is 20-30 mm and its thickness is 3-4 mm. The impeller 2 is formed by injection molding with fiber-reinforced PPS in which a reinforcing material, such as glass fiber, is used. In the injection molding, the glass-fiber-reinforced PPS is in a molten state of high temperature, and the PPS is injected into a mold portion for the base portion 2 a, and passing through that for the vane portion 2 b, then is injected into that for the outer ring portion 2 c.

In this aspect of the present invention, given that a projected area of the entire vane portion 2 b is S1, that of the ring portion 2 c, S2, that of the base portion 2 a, S3, when the impeller 2 is projected from a direction along a motor shaft of the motor rotor 3, the ratio of S3 to S1 is made to fall between 9:1 and 15:1. And the ratio of S2 to S1 is made to fall between 0.10:1 and 0.13:1.

When molding the above-described impeller 2, the glass-fiber-reinforced PPS injected into the mold portion for the base portion 2 a, fills uniformly the portion and then passes, with a constant high pressure, through that for the vane portion 2 b, which can keep, even at the bends, the randomness of fiber orientation relatively high. Then, pressure is removed from the fiber; thereby, the PPS flowing into the mold portion for the outer ring-portion 2 c, from that for the vane portion 2 b also obtains a relatively high randomness of the fiber orientation.

FIG. 3 is a characteristic diagram showing the swelling quantity of the impeller 2 by alcohol and toluene contained in fuel with respect to the ratio of the projected area S3 of the base portion 2 a to the projected area S1 of the entire vane portion 2 b and the ratio of the projected area S2 of the outer ring portion 2 c to the area S1, as a parameter. In the diagram, it is indicated that the swelling quantity is curbed in the region that the value of S3/S1 falls between 9 and 15 and that of S2/S1 falls between 0.10 and 0.13. It is also indicated that the swelling quantities of the vane portion 2 b and the ring portion 2 c can be curbed due to a relatively-high fiber randomness in those portions. Furthermore it is preferably indicated that the swelling quantity is curbed most in the region that the value of S3/S1 falls between 12 and 14 and that of S2/S1 falls between 0.10 and 0.13.

Consequently, because the swelling quantities of the vane portion 2 b and outer ring portion 2 c of the impeller 2, by alcohol and toluene contained in fuel, can be curbed, in a circumferential flow pump 1 provided with an impeller according to Embodiment, the impeller 2 can be prevented from locking without widening the clearance 7 a between the impeller 2 and the pump-housing 7. 

1. A circumferential flow pump that feeds into an internal combustion engine, fuel from a fuel tank, including: a disc-shaped impeller fitted to a motor rotor, and a pump-housing for housing the impeller; characterized in that the impeller is made of fiber-reinforced polyphenylene sulfide and comprises: a base portion fitted to the motor rotor, a vane portion provided outer-circumferentially on the base portion, and an outer ring portion provided outer-circumferentially on the vane portion; and the vane portion comprises a plurality of vanes arranged radially protruding straightly from the base portion and each vane includes a bend; and furthermore, given that a projected area of the entire vane portion is S1, that of the ring portion, S2, that of the base portion, S3, when the impeller is projected from a direction along a motor shaft of the motor rotor, the ratio of S3 to S1 is made to fall between 9:1 and 15:1, the ratio of S2 to S1 is made to fall between 0.10:1 and 0.13:1. 